The present invention relates to a digital multiplexing system and more particularly to protection control apparatus for use therein. Digital multiplexing systems such as utilized with a telephone system provide faster switching capability than presently existing analog telephone systems because of the capability of utilizing digital techniques. However, digital multiplexing systems are extremely complex and a failure of any portion of a multiplexing system can affect its capability to provide the necessary communications link in the telephone system. Consequently, there is a need to insure that the multiplexing system is functioning properly and in addition can provide protection procedures should there be a failure somewhere in the system.
Some prior art systems have utilized the generation and sending of a test code through a multiplexer which is then compared with a stored reference code to verify that the multiplexer is operating properly. Upon the detection of a faulty multiplexer by virtue of the test code, a stand-by redundant multiplexer is activated to provide the necessary multiplexing/demultiplexing capabilities in place of the failed multiplexer.
While generation of a test code and redundancy techniques are known in the art, providing redundancy on a one for one basis becomes expensive, and as a result it would be desirable to provide protection control apparatus that could be utilized for testing multiplexing systems and providing stand-by capabilities without the need for one for one redundancy schemes such as in prior art systems.